Fob pocket, a small pocket in trousers or waistcoats originally intended to hold a pocket watch
Key fob, a medallion used to identify a key ring, or position on the ring
"Fob" is thus sometimes used for various small electronic security token devices
Watch fob, a medallion or ornament attached to a pocket watch to assist in handling

FOB or F.O.B. as an acronym can also mean:

Fall Out Boy
Fecal occult blood, blood present in the feces that is not visibly apparent
"Federal Office Building"", any office building owned or occupied by the US Government
Fetal osteoblast progenitor cell
Follow-on biologics, a term used to describe generic biologics
Forward Operating Base, any secured forward position that is used to support tactical operations
Fractional Orbital Bombardment, a method of nuclear weapons delivery
Incoterm; Free On Board an International Commerce Term
Now obsolete US "Foreign Trade Definitions" of 1941 Freight On Board Fresh off the boat, a slang phrase for people of foreign nationality
FOB (play), a 1981 David Henry Hwang play